This invention relates to extremely high frequency (EHF) and millimeter wave (MMN) amplifiers, and has particular relationship to amplifiers using quasi-optical spatial power combining techniques.
Attention is directed to Wong et al. (including several co-inventors of the present invention), "Bi-Directional Spatial Power Combiner for Millimeter-Wave Solid State Amplifiers" , Work Shop on Millimeter Nave Power Generation and Beam Control, Sep. 14, 1993, the disclosure of which is incorporated by reference. Attention is also directed to U.S. Pat. No., 5,214,394, "High Efficiency Bi-Directional Spatial Power Combiner Amplifier" , issued May 25, 1993, to Sam H. Wong (a co-inventor of the present invention), the disclosure of which is also incorporated by reference.
As shown in FIG. 1 of the present application (which closely parallels FIG. 17 of the '394 patent), vertically polarized incident radiation 10 (especially in the gigahertz range) propagates through a collimating lens 12 to the broad end of a feedhorn 14. The lens 12 directs the incident radiation 10, which has been fed into the narrow end of the feedhorn 14, onto an amplifier array 16. The amplifier array 16 amplifies the incident radiation 10 and re-radiates it, as return radiation 18, back towards the narrow end of the feedhorn 14. The arrows symbolizing return radiation 18 are drawn longer than those symbolizing incident radiation 10 to indicate that return radiation 18 has more power.
The amplifier array 16 is constructed so that return radiation 18 is polarized orthogonally to that of incident radiation 10. An orthomode transducer 20 directs the return radiation 18 to the orthogonal port of the orthomode transducer 20 from the narrow end of the feedhorn 14. A circulator 22, situated on one side of the orthomode transducer 20 opposite the feedhorn 14, prevents feedback of return radiation 18 (and, indeed, leaking incident radiation 10) into the source of the incident radiation 10. An array of parasitic micropatches 24, situated between lens 12 and the amplifier array 16, provides impedance matching.
The '394 device works well, but has narrow bandwidth, because the enclosed horn with conductive walls supports higher order mode resonances.